1. Technical Field
This invention relates to radio telecommunications networks in general and, more particularly, to a method and apparatus for detecting fraudulent telephone usage within such a system.
2. History of Related Art
Fraud has been identified as one of the cellular telephone industry's biggest problems. Because of fraud, the annual global loss in revenue now exceeds $1 billion. This amount does not account for indirect fraud costs, which include anti-fraud in-house personnel teams, the cost of anti-fraud equipment, and the negative impact such fraud has on wary potential subscribers.
Fraud appears in many forms, and new methods of committing fraud are conceived on almost a daily basis. Criminals who steal cellular phone services enjoy anonymity and other benefits, such as the ability to make an unlimited number of free calls, income from selling long-distance services at reduced rates, and the ability to bypass regulations that prohibit communications between certain countries.
Cellular systems are vulnerable to fraud at several points in the network. To date, the elements most frequently used to steal services are the phone itself, the radio interface, and the signaling network. Methods used to defeat the fraudulent use of telephone services are often frustrated by publication of the methods themselves. In fact, the Internet is a popular forum for fraudsters who, in a matter of minutes, are able to post detailed instructions to a global audience on how telephone fraud may be committed.
One of the most popular, and difficult to detect, methods of fraud is cloning, which can be described as the complete duplication of a legitimate mobile terminal, including the mobile identification number (MIN), the electronic serial number (ESN) and, in some cases, the subscriber's personal identification number (PIN). When cellular systems cannot distinguish between a clone and a legitimate subscriber, cloned telephones successfully pass pre-call validation checks, allowing fraudulent use that is billed to legitimate subscribers. In many cases, fraudulent calling activity is not detected until after thousands of dollars of non-recoverable calling charges have accrued.
The MIN-ESN represents a unique combination that may be used to validate a legitimate subscription. When a subscription is activated for the first time, the MIN-ESN are stored in the operator's database, or home location register (HLR). From that time onward, each access request to the MSC by the mobile terminal triggers a matching check by the MSC with the numbers received from the HLR. If the MIN-ESN transmitted by the phone matches the HLR data, then the MSC processes the access request.
The most common way of obtaining MIN-ESN combinations for use in cloning cellular phones is the theft of subscriber data from the operator, via interception, using a frequency scanner over the air interface. Since the MIN-ESN combination is transmitted on the air interface control channel whenever a mobile terminal registers with a Mobile Switching Center (MSC) or initiates/receives a call, the MIN-ESN combination is fairly easy to retrieve. One, if not many, cellular phones can easily be reprogrammed to use new MIN-ESN combinations.
Therefore, a method and apparatus capable of defeating cloned cellular telephone operations which make use of stolen MIN-ESN combinations is desirable. Further, it is also desirable to have a method and apparatus of defeating fraudulent cellular telephone operations which make use of stolen PINs.